The safety of occupants in military vehicles during land mine detonation is an ongoing concern. One way to reduce spinal fracture and thus to improve survivability is to limit the forces transmitted through a seat to its occupant.
Conventionally, this has been accomplished by deploying thick, soft cushions. But the low spring rates of soft cushions permit high speeds to be reached between the occupant and a seat pan in response to a blast. This phenomenon tends to increase the lumbar/pelvic load imposed on the seat occupant. The total thickness of the compressed cushion is ideally minimized. Therefore, careful deployment of other mechanical energy absorbing components is desirable in a crashworthy energy-absorbing seat design.
To reduce the impact between the seat pan and occupant in response to high blast forces, the seat structure must possess sufficient energy absorption capacity before the structure bottoms out.
Ideally, a desirable energy absorber should be light in weight, not take up excessive space and yet still exhibit high specific energy absorption. Preferably, the absorber should respond to an impact with a relatively constant force, resist loads in the opposite direction due to the stroking (rebound), and be relatively insensitive to the rate at which a blow is delivered.
But conventional military and industrial vehicle seat systems may not adequately respond to blast forces transmitted by land mines and other improvised explosive devices. Innovations in vehicle armor alone tend to be insufficient to mitigate blast forces and reduce the incidence of injury to the occupants of, for example, military vehicles that operate in a war zone.
Thus, there is an unfulfilled need for energy absorbing and dissipating structures for effectively resisting blast impulses.
Against this background, it would be desirable to provide an energy-absorbing apparatus and method that:
Has a minimal installed cost;
Is compatible with existing vehicle seats;
Enhances (or does not diminish) the overall appearance of the seat;
Meets all military and vehicle codes and requirements;
Provides additional protection to the seat occupant; and
Requires little or no maintenance.
Among the art considered before filing this application are the following references: “Lumbar load attenuation for rotorcraft occupants using a design methodology for the seat impact energy-absorbing system”, Central European Journal of Engineering, 2012, 562-577; U.S. patent publication No. 2014/0007761; U.S. Pat. Nos. 5,030,501; 6,938,290; 7,574,760; 8,915,339; and 9,279,258.